There's MicroOS from the OpenSUSE corner, including its respins with GNOME or KDE. IIRC that uses BTRFS snapshots/filesystems instead of A/B root filesystems, but same broad idea.

Technically, the Gnome spin is now named Aeon: https://aeondesktop.github.io/

And the KDE version is Kalpa, but they're both still spins of MicroOS.

VanillaOS would be another great example (arguably cooler than silverblue imo).